Add an underscore to flood stage setting

This is a minor nitty bikeshedding change that renames the suffix of the
disk flood stage setting to "flood_stage" from "floodstage".

Relates #25659

buildSrc/src/main/groovy/org/elasticsearch/gradle/test/ClusterFormationTasks.groovy

@@ -314,7 +314,7 @@ class ClusterFormationTasks {
         esConfig['cluster.routing.allocation.disk.watermark.low'] = '1b'
         esConfig['cluster.routing.allocation.disk.watermark.high'] = '1b'
         if (Version.fromString(node.nodeVersion).major >= 6) {
-            esConfig['cluster.routing.allocation.disk.watermark.floodstage'] = '1b'
+            esConfig['cluster.routing.allocation.disk.watermark.flood_stage'] = '1b'
         }
         esConfig.putAll(node.config.settings)
 

core/src/main/java/org/elasticsearch/cluster/routing/allocation/DiskThresholdMonitor.java

@@ -66,7 +66,7 @@ public class DiskThresholdMonitor extends AbstractComponent {
     private void warnAboutDiskIfNeeded(DiskUsage usage) {
         // Check absolute disk values
         if (usage.getFreeBytes() < diskThresholdSettings.getFreeBytesThresholdFloodStage().getBytes()) {
-            logger.warn("floodstage disk watermark [{}] exceeded on {}, all indices on this node will marked read-only",
+            logger.warn("flood stage disk watermark [{}] exceeded on {}, all indices on this node will marked read-only",
                 diskThresholdSettings.getFreeBytesThresholdFloodStage(), usage);
         } else if (usage.getFreeBytes() < diskThresholdSettings.getFreeBytesThresholdHigh().getBytes()) {
             logger.warn("high disk watermark [{}] exceeded on {}, shards will be relocated away from this node",
@@ -78,7 +78,7 @@ public class DiskThresholdMonitor extends AbstractComponent {
 
         // Check percentage disk values
         if (usage.getFreeDiskAsPercentage() < diskThresholdSettings.getFreeDiskThresholdHigh()) {
-            logger.warn("floodstage disk watermark [{}] exceeded on {}, all indices on this node will marked read-only",
+            logger.warn("flood stage disk watermark [{}] exceeded on {}, all indices on this node will marked read-only",
                 Strings.format1Decimals(100.0 - diskThresholdSettings.getFreeDiskThresholdFloodStage(), "%"), usage);
         } else if (usage.getFreeDiskAsPercentage() < diskThresholdSettings.getFreeDiskThresholdHigh()) {
             logger.warn("high disk watermark [{}] exceeded on {}, shards will be relocated away from this node",

core/src/main/java/org/elasticsearch/cluster/routing/allocation/DiskThresholdSettings.java

@@ -50,8 +50,8 @@ public class DiskThresholdSettings {
             new HighDiskWatermarkValidator(),
             Setting.Property.Dynamic, Setting.Property.NodeScope);
     public static final Setting<String> CLUSTER_ROUTING_ALLOCATION_DISK_FLOOD_STAGE_WATERMARK_SETTING =
-        new Setting<>("cluster.routing.allocation.disk.watermark.floodstage", "95%",
-            (s) -> validWatermarkSetting(s, "cluster.routing.allocation.disk.watermark.floodstage"),
+        new Setting<>("cluster.routing.allocation.disk.watermark.flood_stage", "95%",
+            (s) -> validWatermarkSetting(s, "cluster.routing.allocation.disk.watermark.flood_stage"),
             new FloodStageValidator(),
             Setting.Property.Dynamic, Setting.Property.NodeScope);
     public static final Setting<Boolean> CLUSTER_ROUTING_ALLOCATION_INCLUDE_RELOCATIONS_SETTING =

docs/reference/modules/cluster/disk_allocator.asciidoc

@@ -28,7 +28,7 @@ file or updated dynamically on a live cluster with the
     relocate shards once less than the configured amount of space is available on
     the node.
 
-`cluster.routing.allocation.disk.watermark.floodstage`::
+`cluster.routing.allocation.disk.watermark.flood_stage`::
 +
 --
     Controls the flood stage watermark. It defaults to 95%, meaning ES enforces
@@ -91,7 +91,7 @@ PUT _cluster/settings
   "transient": {
     "cluster.routing.allocation.disk.watermark.low": "100gb",
     "cluster.routing.allocation.disk.watermark.high": "50gb",
-    "cluster.routing.allocation.disk.watermark.floodstage": "10gb",
+    "cluster.routing.allocation.disk.watermark.flood_stage": "10gb",
     "cluster.info.update.interval": "1m"
   }
 }